In today's electrical supply systems, there are occasions when alternate sources of electric power are necessary or desirable. For example, the capability of switching from utility power to emergency generator power is extremely important for many businesses, hospitals and industries, and is also being employed in residential applications.
In certain applications, it is desirable for separate electrical circuits or even separate groups of electrical circuits to be arranged so that when one group of circuits is switched to a conductive state, another group of circuits is switched to a non-conductive state in alternating fashion. In some arrangements, it may be desirable to alternately switch a common load between separate power sources, so that as one power source is disconnected from the load, the second power source is connected after a negligible delay, to prevent any or minimal interruption of power to the load. In order that the desired period of alternate switching may be effective essentially simultaneously, a need has been recognized to employ a coupling mechanism which functions to switch one group of circuits OFF as the other group of circuits is switched ON.
One type of interlock for first and second tandemly aligned circuit breaker switches having first and second operating handles thereon is disclosed in U.S. Pat. No. 5,648,646 issued Jul. 15, 1997 to Flegel. In the '646 patent, the interlock includes a linkage arrangement in the form of first and second link members for applying a linear force between the first and second operating handles. Each of the operating handles defines a pair of oppositely facing sides which receive fasteners for connecting the link members thereto. A pair of retainer members aligns and maintains the fasteners in the operating handles. Each link member is provided with at least one slot and is connected to the first operating handle such that the first link member is disposed adjacent one of the oppositely facing sides of the first handle, and the second link member is disposed adjacent the other of the oppositely facing sides of the first handle. Further, each link member is connected to the second operating handle such that the first link member is disposed adjacent one of the oppositely facing sides of the second handle, and the second link member is disposed adjacent the other of the oppositely facing sides of the second handle. The link members are constructed and arranged such that pushing the first operating handle from an OFF position to an ON position pushes the second operating handle from an ON position to an OFF position.
While the above-described linkage arrangement operates satisfactorily, it remains desirable to provide a more simplified and economical mechanism which automatically turns one circuit breaker OFF when an adjacent circuit breaker is turned ON. Such a mechanism should assure that the main contacts of both circuit breakers cannot be closed at the same time. It is also desirable that this mechanism does permit, however, both of the circuit breakers to be switched OFF at the same time.